This application claims the benefit of Korean Patent Application No. 2000-81493, filed on Dec. 26, 2000, which is hereby incorporated by reference as if fully set forth herein.
1. Field of the Invention
The present invention relates to a fabrication method of a liquid crystal display device, and more particularly to a method of temporarily fixing an attachment state of upper and lower substrates before a hot press process for hardening.
2. Discussion of the Related Art
Generally, liquid crystal display (LCD) devices include upper and lower substrates, where color filters and thin film transistors (TFTs) are disposed. A liquid crystal layer is interposed between the upper substrate and the lower substrate. Transmittance of the LCD devices is controlled by applying a voltage to common electrodes and pixel electrodes so that characters and images are displayed with a light shutter effect.
A fabrication process of a liquid crystal cell will be explained briefly.
After the upper and lower substrates are aligned and attached so that the surfaces of the common electrodes and pixel electrodes face each other, the liquid crystal material is injected between the substrates and an injection hole is sealed. Polarizers are then attached on each outer surface of the upper and lower substrates.
The fabrication process of the liquid crystal cell seldom includes repeated steps compared with the fabrication processes of the TFT and the color filter. The process includes forming an orientation film, forming a cell gap and cutting the cell.
FIG. 1 is a flow chart illustrating a conventional fabrication process of a liquid crystal cell.
At step ST1, a lower substrate is prepared by forming an array of TFTs and pixel electrodes on the lower substrate.
At step ST2, an orientation film is formed on the lower substrate. Formation of the orientation film includes depositing a polymeric thin film and subsequently performing a uniform rubbing process. The rubbing process determines an initial alignment direction and supplies the normal operation of the liquid crystal layer and the uniform display characteristic of the LCD device. Typically, an organic material of the polyimide series is used as the orientation film. The rubbing method includes rubbing the orientation film along the specific direction with a rubbing cloth, thereby aligning the liquid crystal molecules along the rubbing direction.
At step ST3, a seal pattern is formed on the lower substrate. In the liquid crystal cell, the seal pattern serves two functions: forming a gap for liquid crystal material injection and confining the injected liquid crystal material. The seal patterning process forms a desired pattern by application of a thermosetting plastic. A screen-printing method using a screen mask is typically used for this process.
At step ST4, a spacer is sprayed on the lower substrate. The size of the spacer used in the liquid crystal cell maintains a precise and uniform gap between the upper and lower substrates. Accordingly, the spacers are uniformly sprayed on the lower substrate.
At step ST5, the upper and lower substrates are aligned and attached. The alignment margin between the upper and lower substrates is determined by the device design, and accuracy within a few micrometers is generally required. If the alignment margin is exceeded, the liquid crystal cell will not operate adequately due to light leakage.
At step ST6, the attached liquid crystal substrate is divided into unit cells. Generally, a plurality of unit cells are formed on a large sized glass substrate and then divided through a cutting process. In the fabrication process of the initial LCD devices, the unit cells are separated after simultaneous injection of the liquid crystal material into the unit cells. However, injection of liquid crystal material is commonly performed after a large sized liquid crystal substrate is cut into unit cells due to an increase of the cell size. The cell cutting process includes a scribe process that forms cutting lines on a surface of the substrate using a diamond pen, a hardness of which is higher than that of the glass substrate, and a break process that divides the substrate by force.
At step ST7, a liquid crystal material is injected into the unit cells. The unit cell has a size of several hundred square centimeters with a gap of several micrometers. Accordingly, a vacuum injection method using pressure difference between the interior and exterior of the unit cell is commonly used as an effective injection method.
In the previous process, the seal pattern is hardened under high temperature and the upper and lower substrates are not firmly attached before hardening. Therefore, temporarily fixing the substrates before a hot press process for hardening is required. Means to support the upper and lower substrates (for convenience, called as a fixing means) with a specific shape are formed at all four corners of the lower substrate between the seal patterning and attachment processes. Light curable resin can be used as the fixing means.
However, during the fabrication process of the LCD device, a residual photoresist remains at the four corners so that residual thin film layers can also remain at the four corners. Since the light curable resin is located on the residual thin film layers, the light is partially screened by the residual thin film layers and the light curable resin is not hardened completely so that a misalignment of the upper and lower substrates can occur in the hot press process.
Accordingly, the present invention is directed to a liquid crystal display device and manufacturing method thereof that substantially obviates one or more of problems due to limitations and disadvantages of the related art.
An advantage of the present invention is to provide a liquid crystal display device and a manufacturing method thereof that can prevent a drawback of attachment in a hardening process.
Additional features and advantages of the invention will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a method of fabricating a liquid crystal display device includes preparing upper and lower substrates; forming an array pattern of thin film transistors on the lower substrate; depositing a thin film layer on the entire lower substrate except for four corners by using a shadow mask; forming a seal pattern on the lower substrate; forming an attachment resin at each of the four corners of the lower substrate, forming a color filter and a black matrix on the upper substrate; attaching the upper and lower substrates and hardening the attachment resin by exposing the resin to light.
In another aspect, a method of fabricating a liquid crystal display device includes preparing upper and lower substrates; forming an array pattern of thin film transistors on the lower substrate; forming a seal pattern on the lower substrate; forming an attachment resin at each of the four corners of the lower substrate; forming a color filter and a black matrix on the upper substrate except for the four corners; attaching the upper and lower substrates; and hardening the attachment resin by exposing the resin to light, wherein the light is irradiated from an outer side of the attached upper and lower substrates.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.